SSHscan.py will allow you to scan a internal network through a SSH with port forwarding enabled. The tool allows to create a port forward in localhost for every open port detected in the internal network range.

This tool is not one that can be used in every engagement but when you have the opportunity and the need it will came handy.

The tool has been included in the edgeSSH kit, where we will include all the scripts related with SSH, at the moment only bruteSSH, a SSH login bruteforcer and scanSSH are included in the kit.

You can download the code here: http//code.google.com/p/edgessh

Command line options:
 
       -h: target host
       -u: username
       -p: password
       -l: targets lists to scan
       -t: threads
       --remote-host: host to scan
       --remote-ports: port list to scan
       --default-ports: scan default ports
       --all-ports: scan all 65535 ports
       --keep-tunnels: Forward all open ports

Examples:

    scanssh.py -h 192.168.1.55 -u root -p passowrd -t list.txt
    scanssh.py -h 192.168.1.55 -u root -p password --remote-host 127.0.0.1 --remote-ports 80,443
    scanssh.py -h 192.168.1.55 -u root -p password --remote-host 127.0.0.1 --default-ports

[source: http://edge-security.blogspot.com/2011/06/scanning-ports-through-ssh-port.html]

Related posts:

1. Port Forwarding for Windows
2. Pivoting to Internal Network using Plink and Fpipe by Exploit.co.il
3. Vulnerability scanning with OpenVAS
4. Digging tunnels with SSH
5. Ncrack – Remote Desktop Brute Force Tutorial